The subject invention is directed toward the art of regenerative heat exchange systems and, more particularly, to a regenerative incinerator system.
The invention is particularly suited for use in fixed bed regenerative incinerator systems and will be described with particular reference thereto; however, the invention is capable of broader application and could be used in a variety of such systems.
Fixed bed regenerative incinerator systems are commonly used to remove contaminants such as odors, impurities, and noxious off-gases from air exiting from various manufacturing processes. The systems perform the removal process by subjecting the contaminants to sufficient heat and oxygen to cause them to oxidize.
Systems of this general type are shown, for example, in U.S. Pat. Nos. 3,895,918 and 3,870,474. Generally, the systems include two or more fixed bed regenerative heat exchangers connected to a common combustion or incinerator chamber. The contaminant laden air is conducted through one of the heat exchangers where it is heated. Thereafter, it is conducted to the combustion chamber where the contaminants are burned and completely oxidized, generally with the addition of a hydrocarbon fuel. The hot combustion gases are then exhausted through another of the heat exchangers where they give up a major portion of their heat content before being discharged to the atmosphere.
Periodically, flow through the system is reversed. The incoming contaminate laden air is then heated by the heat exchanger which was previously heated by the exiting combustion gases, and the heat exchanger previously cooled by the incoming air is reheated by the exiting combustion gases.
The amount of hydrocarbon fuel which must be introduced into the combustion chamber depends to a large extent on the amount of heat released by the combustible contaminants in the incoming air stream. For example, when the systems are used to eliminate organic solvent vapors, the incoming air stream can easily contain enough solvent vapors to make the process self-sustaining. That is, the required combustion takes place without the need to supply additional fuel to the combustion or incinerator chamber. In fact, a problem often encountered is that the total energy content in the solvent vapors can be such as to cause the system to exceed its maximum operating temperature and go out of control, thereby requiring shut-down.
The prior art has proposed several methods and apparatus for dealing with the noted problem. One method has been to increase the volume of air passing through the unit so that the additional air will absorb the excess heat generated by the excess solvent. A second method has been to bleed gases from the combustion chamber before they enter the downstream or exit heat exchanger. This allows a desired level of heat exchange to be maintained on the entry heat exchanger. A third method has been to purge each heat exchanger with fresh outside air with each reversal of flow. The method results in cooling each heat exchanger to thereby reduce the ultimate maximum temperature reached during operation.
While the approaches discussed have somewhat alleviated the problem, they have not been entirely satisfactory. For example, increasing air flow through the units and fresh air purging generally require increasing the size of various components to handle the increased air flow, as well as the installation of additional air blowers, etc. In addition, with these prior systems it is not, of course, possible to control mass flow through the system.